WHACKY WHIZZERS

Showing posts with label learning. Show all posts

Fridge magnet from hard drive

Posted by gautam Labels: fun, hardware, learning

Earlier i had posted a video of obtaining a magnet from an old hard drive.
Link to the older post: 5 minute projects from Popsci

So i had a old damaged hard drive so i gave it a try:

This how my hard drive looks from outside

The problem was that i had a screw driver but the screws on the hard disk were hexagonal in shape
So i had to buy a TORX SET costing about 150-200 Rs

I unscrewed all the screws the result was i could see the inside of the hard disk

and ......
in the end i managed to remove a magnet for putting stuff on my fridge from the hard disk

NSIT-IEEE

Posted by rahul Labels: learning

NSIT has developed exponentially over the past few years and specially the NSIT branch of IEEE has grown so widely that now its no more a minority society in the college. In fact the membership just doubled in a span of 3 months. This was indeed a great achievement for the society.the official website can be viewed here

STEPPER MOTOR

Posted by gautam Labels: geeky, learning, robotics

The most common problem we face when we use normal DC motors is that we don’t have precise control over how much it rotates. To rotate DC motors through a particular number of degrees what we can do is either calibrate it for a delay based operation i.e. if I switch it on for n seconds it moves 360 degrees; or what we can do is attach n encoder to the shaft which gives us a feedback on how much the motor shaft has rotated so that we can stop it when it rotates through the desired angle. Home made encoders give good results but don’t have such a high resolution and high resolution encoders are costly.
In such cases where we need to control the rotary position of the motor we can use stepper motors. Stepper motors have a tendency to make beginners feel uncomfortable about using them. But lets hope this air of discomfort about using stepper motors disappears once we are done through this article.
Stepper motors are motors available in round, square, rectangular shapes with 4 or more wires coming out of them.

In the permanent magnet stepper motor the rotor is a permanent magnet and the stator is a set of coils which are energized one after another. In the unipolar motors the direction of current in the coil doesn’t reverse (so UNI) while in the bipolar the current through the coil flows in both the directions (so BI).In both types of stepper motors there are two coils wound on the stator poles, which gives us 4 wires.

The difference is that in unipolar motors there is a center tap from each of the coil winding. These center taps are either brought out individually (which will give us 4+2 = 6 wires) or are shorted together and brought out (which gives us 4+1 = 5 wires)

Properties:

1) Digitaly controlled brushless motor that rotate a specific number of degrees (a step).
2) Number of degrees (resolution) can be between .72 to 90 degrees. General purpose steppers have a resolution of 15 or 30 degrees a step.
3) High precision, low torque.

The following figure shows a stepper motor deflected by 90 degrees

This occurs only when one coil is excited and other's are not.

The following figure shows half step where two adjacent coils are excited and therefore the rotor moves in between the coils .

By this we can move by 45 degrees.

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IR Sensors

Posted by gautam Labels: geeky, learning, robotics

The Infrared emitter detector circuit is very useful if you plan to make a line following robot, or a robot with basic object or obstacle detection. Infrared emitter detector pair sensors are fairly easy to implement, although involved some level of testing and calibration to get right. They can be used for obstacle detection, motion detection, transmitters, encoders, and color detection (such as for line following).

Line sensor:

In order to detect a line, we use the principle of reflection of light over different colors. As we all know, a white color object reflects almost all light incident on it while a black colored object absorbs all. Now, by measuring the variation in the intensity of reflected light we can easily determine the presence/absence of line under the sensor.

AMPLIFIED SENSOR CIRCUIT

Description:

The circuit uses an comparator to compare the value detected and ouput logic ‘1’ or ‘0’ or ON and OFF.

We use an IR LED which will emit Infrared light and it will be reflected by the surface. The detector acts as a variable resistor whose value depends on the intensity of light falling on its surface. The higher the intensity, the lower is the resistance of the detector. The detector and R2 act as a potential divider. When the intensity is high (reflected from white surface), the resistance of detector is low and so the value of the potential is high. Similarly when the intensity is low (reflected from black surface), the resistance of the detector is high and so the potential is low.

This potential is compared with a reference potential. The reference can be varied by the potentiometer (pot). Calibration is required. You have to record potentials of the white as well as black surface and then find their ranges. According these potentials ten set the reference so that for white surface output is .high and for white black surface output is low.

An LED can also be used as a visual detector so that you can see whether the surface is black or white.

R3 resistor prevents excessive current to pass through the LED. The value of the resistor depends on the size and the colour of the LED. More the diameter of the LED , more is the current it will sink in. R1 should be chosen according to the LED. Usually for 3mm Red LED and 5V supply 330Ω is enough. R2 should be larger then the maximum resistance of the detector.

THINGS TO NOTE:

The LED and detector have very narrow emission and detection angles, so keep them close so that the circuit functions properly.
Metallic or glossy surfaces reflect more tend to reflect more light, so make sure you calibrate the device properly.
Many objects are opaque to visible light (that means light doesn't pass through it, like wood, black plastic, metal), but are transparent to IR light.
If you work in the sunlight make sure it doesn’t interfere with the function of the circuit. Usually sensors placed below the body of the robot are the least affected by it.
Depending on resistor values, your IR circuit can be tweaked to better detect color instead of distance.

How To make a H-Bridge for a motor

Posted by gautam Labels: learning, robotics, videos

Hey Innovision is coming
HERE is the link for this year's site http://www.innovision07.com/index.php

All those who are participating in carnage and/or robowars will find this interesting

This is a hack which helps in fast change of direction of DC motor which can help in fast switch
between forward and backward direction

An H-bridge is a type of circuit that you can use to get a reversible DC motor to spin both clockwise and counterclockwise.

In other words, this circuit allows you to quickly reverse the direction a motor is spinning by using a switch or controller chip to change its direction.

I'm going to show you how to make the simplest and most reliable form of H-bridge that I know how to make. I must warn you that this is by no means the best H-bridge design and, in fact, it has a couple shortcoming which I will explain later.

Although, should you never have made an H-bridge before or simply need a circuit that can reverse the direction of a motor's spin, then this circuit is a quick and easy solution.

This is the link to the instructions to make a H-Bridge http://www.instructables.com/id/EQDILA2F54HOEGE/

Here is the link where the working of the H-Bridge is shown

GREAT BURNING LASER HACK

Posted by gautam Labels: hardware, learning, videos

Laser Flashlight Hack! - The best free videos are right here

DARPA Urban Challenge 2007

Posted by Pankaj Chopra Labels: games, learning, robotics

The robotics community is ready to tackle vehicle operation inside city limits.

The Defense Advanced Research Projects Agency (DARPA) will hold its third Grand Challenge competition on November 3, 2007.
DARPA will award prizes for the top three autonomous ground vehicles that compete in
a final event where they must safely complete a 60-mile urban area course in fewer than six
hours. First prize is $2 million, second prize is $500,000 and third prize is $250,000. To
succeed, vehicles must autonomously obey traffic laws while merging into moving traffic,
navigating traffic circles, negotiating busy intersections and avoiding obstacles.

The location of the event will be announced on August 9,2007 after the qualification process is complete. The course will involve a 60-mile (96 Km) urban area course, to be completed in less than 6 hours. Rules will include obeying all traffic regulations while negotiating with other traffic and obstacles and merging into traffic.

The Urban Challenge requires designers to build vehicles able to obey all traffic laws while they detect and avoid other robots on the course. This is a particular challenge for vehicle software, as vehicles must make "intelligent" decisions in real time based on the actions of other vehicles.

The winner will receive US$2 million. The second place finisher will receive US$1 million and the third place finisher will receive US$500,000.

The event is being followed closely by auto manufacturers for the implications it holds for smarter cars and safer highways in the future.

We hope to send a team from India for the DARPA challenge in coming years.